An electric drive can include at least a power stage, a control means for controlling the power stage, and a load, the operation of which is controlled by the power stage and the control means thereof. The power stage and its control are herein referred to as a frequency converter. At its simplest, such an arrangement may be, for instance, a motor that is rotated by a frequency converter, which is controlled by a control card. If necessary, power stages may be connected in parallel to control the same load. The power stages may thus be controlled by the same control means.
In certain processes, a high-power frequency converter including a plurality of power stages may be used for controlling one heavy load for some time, and when this heavy load is not needed, the same power stages may be utilized for providing a plurality of lower power frequency converters. It is thus not necessary to provide each load with its own frequency converter. This saves costs and space.
However, it is difficult to manage such an arrangement by applying known techniques. The configuration of various combinations of control means and electric machines may be complicated and subject to errors.